Studies On Fresh-keeping And Postharvest De-Astringency Handles Of Persimmon Fruits

At room temperature, Persimmon fruits are prone to rot, browning and softening duringstorage. The key to keeping the persimmon storage and process quality is to keeppersimmon fresh, crisp and good de-astringent process. This research starting from choosingthe optimum storage temperature of persimmon, studied effects of the ethylene absorbentand CaCl2aqueous solution soaking to the quality of persimmon, and researched effects ofthree methods: warm water, alcohol and CO₂to eliminate the astringent of persimmon. Themain results are as follows:1For choosing the best temperature in the storage, the effects in different temperatures（0℃,2℃,4℃and6℃） on the quality of the persimmon were studied according to theindices about fruit appearance quality, respiratory intensity, weight loss rate, Vc content,soluble sugar content, and titratable acid. It preliminarily showed that the persimmon storedat0℃～2℃maintained better color and higher hardness and had lower respiratory intensity,weight loss rate and contained more Vc content, titratable acid, soluble sugar content thanthat at the other conditions.2The ethylene absorbent and CaCl2aqueous solution soaking were used to maintain thehardness of persimmon, which found that fruit could maintain good colour and lustre,reduced the softening of persimmon, kept more Vc, titratable acid, soluble solids, delayedthe soluble tannin translating to insoluble tannins, kept the cell membrane permeability,reduced the MDA accumulation.The result showed that the process could maintain goodquality of persimmon effectively.3Study on the best treat of de-astringent processes of persimmon by warm water, alcoholand CO₂.The effects of different de-astringent processes on the persimmon quality werestudied according to the indices of the soluble tannin content, hardness and soluble solidcontent.The results showed that the temperature and time had significant differences in allde-astringent processes. When alcohol concentration was more than20%, there was nosignificant differences on de-astringent processes. When the concentration of CO₂was more than60%, there was no significant differences on de-astringent processes.Using40℃warm water, we could eliminate the astringent completely in1day, and kept high hardness.One disadvantage was that the soaked persimmons in warm water were prone to burst.When we applied alcohol eliminating the astringent completely, the hardness would havefell below0.1MPa, extremely soft. The speed of eliminating the astringent was slower, itwasted at least3days.If alcohol concentration was more than35%, the fruit peel would beprone to shrink. Fresh persimmon could de-astringent completely by70%CO₂at40℃for2days, which could keep better intrinsic quality and appearance of persimmon.So, we caninclude that eliminating the astringent with CO₂was an effective method.4The optimization research on the treatment condition of eliminating the astringent withCO₂.Based on the single factor experiments of eliminating the astringent with CO₂, thesoluble tannin content, hardness were served as indices according to the response surfacedesign to eliminate the astringent with CO₂. We got two quadratic regression equationsabout CO₂concentration, temperature and time. In the regression equations, the impact onthe soluble tannin content in order as: temperature> time> CO₂concentration, the effect onthe hardness of the order as follows: time> temperature> CO₂concentration. The resultsshowed that: the optimum condition of eliminate the astringent was70.49%CO₂,34℃eliminate the astringent for1day. In actual eliminating the astringent for production, indifferent CO₂concentration, different temperature conditions, at any time, we can predictthe situation of eliminating the astringent through the regression equations, so as to meet theproduction needs, to guide the actual production.